As is known, a phase transition takes place when e.g. under the action of heat or pressure reduction vapours segregate from a solution. However, a phase transition is also an inverse course of the aforesaid process where vapours are condensed by means of heat abduction, or are caused to be absorbed by a solution. Mutually opposite phase transitions occur, for instance, in phase transition compartments of the work chambers of multi-effect and multi-flash evaporators, sorption-type refrigerators and heat pumps.
Known heat-engineering apparatus of such destination consist, as a rule, of cylindrical vessels or receptacles, pipe bundles and of extensive pipings connecting various units of the apparatus which permit, therefore, an exployment of expensive conventional manufacturing technologies only. Moreover, due to the variety of employed units the work chambers of the known heat-engineering apparatus of the above mentioned type are anything but compact. This, on the one hand, entails undesired temperature- and pressure losses thus unfavourably affecting the efficiency of the apparatus and, on the other hand, disadvantageously increases their space requirements.
Such difficulties have partly been mitigated by an introduction of heat exchangers in the form of casings or boxes. Such casings are constructional units formed by pairs of confining plates the mutual distances of which are fixed by spacers therebetween. The spacers may be protuberances embossed from confining plates, or inserts like packings disposed between them, or else optional combinations of such expedients.
Employing heat-exchangers of this type has the obvious advantage that a considerable portion of the heat-engineering apparatus, more particularly its heat-exchangers are enabled to be prepared in mechanized mass production by means of up-to-date manufacturing technology. As an example reference may be taken to the single-stage evaporating and condensing plant "Typ JWP-36" of the firm .alpha.-Nirex-Alfa-Laval-Gruppe for delivering a fresh water supply of maritime vessels.
In this known heat-engineering apparatus evaporation of sea water and condensation of vapours /actually steam/ generated thereby, respectively, occurs in a pair of groups of casings abutted groupwise against one another. A pair of adjacent casings have a common confining plate which provides for a heat-transfer relationship therebetween. The two groups of casings are disposed above one another in the enclosure of a cylindrical receptacle. Casings enclosing phase transition compartments are open towards the interior of the receptacle so as to enable vapours to flow from one group of casings into the other one. Thus, a work chamber of the known heat-engineering apparatus under discussion consists of three portions in that its phase transition compartments in the casings communicate with one another through the room enclosed by the receptacle which functions as a transition or third compartment. Consequently, the receptacle is an indispensable part of the apparatus without which its object that is evaporation and condensation or mutually opposite phase transitions cannot be obtained. However, the receptacle which, necessarily, has to be sized for the pressure prevailing in the work chambers of the apparatus can obviously be prepared by means of conventional manufacturing technology only. Thus, such known heat-engineering apparatus are, partly, still unsuitable for mechanized mass production.